Discharge tube



Patented May 24, 1932 sra'ras wal a v T. r. normms'swonrn, or

YORK, N. Y.

nrscmmdn roan No Drawing. Application filed January 8,

It is well known that in electric discharge vessels or tubes containing rare gases such as neon, helium. or the like, the potential. drop can be reduced by making the electrodes, or at least the cathode, of an alkali metal or 0 an alloy thereof, so that the ordinary voltages of 110 or 220 volt will be suflicient for the operation of such discharge tubes.

By Austrian Patents Nos. 69,696, 74,448 and 74,449 it has further become known that for the purpose of reducing the cathode drop it is by no means necessary that the electrodes consist of an alkali metal or of an alloy 0 such metals, but that it is suflicient to make a deposit from vapors of the alkali metals at some place in the interior of the discharge vessel, preferably within the region of the electrodes while the electrodes as such may consist of any desired light or heavy metal, such as aluminium, nickel, tungsten'or the like. Such discharge vessels may be operated on the ordinary low voltages. The introduction of vapors of the alkali metals into the discharge vessels causes considerable difiiculty, however, and the object of the present invention is a process by which the production of such a deposit is greatly facilitated. 7

According to the present process a mixture of a compound or compounds of one or several alkali metals with one or several suitable reduction agents is introduced into the interior of the discharge vessel and, prior to, or after closing sai vessel, a reaction is caused in this mixture by heating. Thereby vapors of alkali metal are formed which are deposited within the vessel.

The discharge vessel, e. g. an electric rare gas lamp or luminous discharge tube is produced in the usual manner; the electrodes may be made of n'ckel for example. Prior to the exhaustion of the vessel a small quantity of a mixture, for example, of potassium oxide with metallic magnesium is introduced into the discharge vessel and preferably 1927, Serial No.

the vapors produced by the reaction are 158,833, and in Austria September 27,- 1926.

placed on one of the electrodes whereupon the vessel is exhausted and filled-with a rare gas or a mixture of such gases until the desired pressure is reached. The vessel may next be sealed and the deposit produced afterwards, or, vice versa, the' deposit may be produced first, and the vessel then sealed. The deposit is produced in such a manner that the mixture placed in the interior of the vessel is caused to react by heating. In this reaction the magnesium combines with the. oxygen of the potassium oxide, freeing vapors of potassium which are deposited within the vessel, leaving magnesium oxide behind. Inasmuch as magnesium oxide has a very high melting point it causes no disturbance during ordinary operation. matter of course, it is advisable to make said mixture in molecular proportion The heating of the mixturemay be eflected in difierent ways, e. g. by placing an induction coil carrying high frequency current, over the discharge vessel in the region where the mixture was placed, that is to say, preferably in the region of the electrode, whereby heatingis efiected by the inductive action of the high frequency current.

The mixture in which reaction is to be caused, may consist of two or more compounds of the various alkali metals in which case alloys of these metals are formed whim eposited. The reduction agents are generally such substances as, after the reaction form compounds that do not disturb the normal operation of the discharge vessel.

What I claim and desire to secure by ters Patent is: e

1. The method of introducing pure alkali metal into an electric illuminating lampoperating by glow discharge in rare gas cold electrodes, for the purpose of reducing the potential drop, which consists in placing upon the surface 0 a metal member within the lamp :1 mixture consisting of an oxide of I between of weight. p

Leth at least one alkali metal with at least one reducing metal the oxide of which is stable and substantially non-volatile at the operating temperature of the lamp, and heating said 5 metal member sufiiciently to release alkali metal vapor into the tube while the other reguction product remains on said metal memer. v

2. The method of introducing pure potassium into an electric illuminating lamp operating by glow discharge in rare gas between cold electrodes for the purpose of reducing the potential drop, which consists in placing on an electrodea mixture of potassium oxide and magnesium metal, and heating said electrode suficiently to release alkali metal vapor.

In testimony whereof, I have hereunto afed my signature. I ANTON LEDERER. 

